Displacement varying structure of variable displacement compressor

ABSTRACT

A control valve includes a separation portion, which is part of a rod, blocks a through hole that connects a valve chamber and a second chamber with each other. Therefore, the pressure of the second chamber is not directly affected by changes in the opening degree of the control valve. The second chamber and a valve hole forming a part of the through hole are both connected to a second pressure zone through an upstream section of a supply passage. This prevents creation of pressure difference between the valve hole and the second chamber, and thus prevents entry of foreign particles in sliding portions between the through hole and the rod.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a displacement varying structureof a variable displacement compressor. A typical variable displacementcompressor is installed in a refrigerant circuit of a vehicle airconditioning system and changes the displacement based on the pressurein a crank chamber. A displacement varying structure controls thepressure in the crank chamber of the variable displacement compressor.

[0002] Some variable displacement compressor have a control valve calledpressure sensing valve (for example, refer to Japanese Laid-Open PatentPublication No. 2001-173556).

[0003] As shown in FIG. 6, a supply passage 113 connects a crank chamber111 with a discharge chamber 112 of a variable displacement compressor.A valve chamber 102, which forms part of the supply passage 113, isdefined in a housing 101 of the control valve. The valve chamber 102 isconnected to the crank chamber 111 by a downstream section of the supplypassage 113. The valve chamber 102 accommodates a valve body portion 103a of a rod 103. The valve body portion 103 a can be displaced in thevalve chamber 102. In accordance with its position in the valve chamber102, the valve body portion 103 a adjusts the opening degree of thesupply passage 113.

[0004] A pressure sensing chamber 104 is defined in the valve housing101. A pressure sensing member 105, which is a bellows, is located inthe pressure sensing chamber 104. The pressure sensing member 105divides the interior of the pressure sensing chamber 104 into a firstchamber 104 a and a second chamber 104 b.

[0005] A separation wall 106 is provided in the valve housing 101. Theseparation wall 106 separates the second chamber 104 b from the valvechamber 102. A through hole 107 is formed in the separation wall 106.The through hole 107 extends between the valve chamber 102 and thesecond chamber 104 b. The rod 103 extends through the through hole 107and is coupled to the pressure sensing member 105.

[0006] The rod 103 has a separation portion 103 b that is provided atthe end adjacent to the pressure sensing chamber 104. The separationportion 103 b disconnects the valve chamber 102 from the second chamber104 b. The rod 103 also has a coupler portion 103 c, that couples theseparation portion 103 b with the valve body portion 103 a. The diameterof the coupler portion 103 c is less than the diameter of the throughhole 107. Therefore, this section of the through hole 107 functions as avalve hole 107 a that forms part of the supply passage 113.

[0007] A fixed restrictor 114 is in the refrigerant circuit.Specifically, the fixed restrictor 114 is located in a dischargepressure zone. The first chamber 104 a of the control valve is connectedto the discharge pressure zone at a position upstream of the fixedrestrictor 114. The second chamber 104 b of the control valve isconnected to the discharge pressure zone at a position downstream of thefixed restrictor 114. The pressure difference between a section upstreamof the fixed restrictor 114 and a section downstream of the fixedrestrictor 114 represents the flow rate of refrigerant in therefrigerant circuit. Therefore, the pressure sensing member 105 isdisplaced according to changes of the refrigerant flow rate in therefrigerant circuit. The position of the rod 103 (the valve body portion103 a) is determined such that the displacement of the variabledisplacement compressor is changed to cancel the changes in therefrigerant flow rate.

[0008] However, the valve hole 107 a of the control valve is connectedto the discharge pressure zone (discharge chamber 112) of therefrigerant circuit at a position upstream of the fixed restrictor 114through an upstream section of the supply passage 113. That is, thevalve hole 107 a is connected to a section of the discharge pressurezone that is the same as the first chamber 104 a and different from thesecond chamber 104 b.

[0009] Therefore, the pressures in the valve hole 107 a and the secondchamber 104 b, which are adjacent to each other with the separationportion 103 b of the rod 103 in between, are different. This pressuredifference can cause foreign particles to enter the sliding sections ofthe through hole 107 and the rod 103 (the separation portion 103 b).Foreign particles between the through hole 107 and the rod 103 can causethe rod 103 to malfunction.

[0010] To eliminate such a drawback, Japanese Laid-Open PatentPublication No. 2001-173556 discloses another structure shown in FIG. 7that is different from the structure shown in FIG. 6. In the controlvalve shown in FIG. 7, the rod 103 has no structure corresponding to theseparation portion 103 b. Further, the second chamber 104 b is used aspart of the supply passage 113. The space between the through hole 107and the rod 103 (the coupler portion 103 c) functions as part of thesupply passage 113 and is always open to the second chamber 104 b.However, in this case, at the instant at which the valve body portion103 a is displaced to change the valve opening degree, the pressure inthe second chamber 104 b is directly influenced by the change in thevalve opening degree and is changed. This prevents the pressure sensingmember 105 from accurately determining the position of the valve bodyportion 103 a, which adversely affects the control of the displacement.

[0011] Particularly, the compressor shown in FIG. 7 is a “variabletarget pressure difference” type, in which position of the rod 103 (thevalve body portion 103 a) is determined by the equilibrium of the forceof the pressure sensing member 105 and electromagnetic force of anelectromagnetic actuator (not shown). This worsens the controllabilityof the displacement of the compressor shown in FIG. 7. Specifically, theelectromagnetic force of the electromagnetic actuator is sometimeschanged abruptly by an excessive degree. In such a case, the valve bodyportion 103 a is displaced abruptly by an excessive degree. This createsa sudden and excessive change in the pressure in the second chamber 104b.

SUMMARY OF THE INVENTION

[0012] Accordingly, it is an objective of the present invention toprovide a displacement varying structure of a variable displacementcompressor, which structure prevents a rod from malfunctioning and thecontrollability of the displacement from deteriorating.

[0013] To achieve the above objective, the present invention provides adisplacement varying structure of a variable displacement compressor.The compressor is installed in a refrigerant circuit. The refrigerantcircuit has a discharge pressure zone and a suction pressure zone. Thevariable displacement compressor has a crank chamber The displacementvarying structure is capable of varying a displacement of the variabledisplacement compressor by changing a pressure of the crank chamber. Thedisplacement varying structure includes a supply passage for connectingthe crank chamber with the discharge pressure zone. A bleed passageconnects the crank chamber with the suction pressure zone. A controlvalve is located in a control passage. The control passage is one of thesupply passage and the bleed passage. The control valve includes a valvehousing defining a valve chamber, a valve hole, and a pressure sensingchamber. The valve chamber and the valve hole form a part of the controlpassage. A valve body is accommodated in the valve chamber. The valvebody is capable of being displaced. The valve body adjusts an openingdegree of the valve hole in accordance with the position of the valvebody in the valve chamber. A pressure sensing member is accommodated inthe pressure sensing chamber. The pressure sensing member divides thepressure sensing chamber into a first chamber and a second chamber. Thepressure sensing member is capable of being displaced in accordance witha pressure difference between the first chamber and the second chamber.A separation wall separates in the valve housing the valve chamber andthe pressure sensing chamber from each other. The separation wall has athrough hole for connecting the valve chamber and the second chamberwith each other. A rod extends through the through hole and connects thepressure sensing member and the vale body with each other. The rod has aseparation portion that blocks connection between the valve chamber andthe second chamber through the through hole. An adjacent zone isadjacent to the second chamber with the separation portion in between.If a part of the through hole that is closer to the valve chamber thanthe separation portion and opens to the valve chamber forms the valvehole, the valve hole is the adjacent zone. If the valve hole is locatedat the opposite side of the valve chamber with respect to the secondchamber, the valve chamber is the adjacent zone. The adjacent zone andthe second chamber are connected to a common pressure zone in therefrigerant circuit.

[0014] Other aspects and advantages of the invention will becomeapparent from the following description, taken in conjunction with theaccompanying drawings, illustrating by way of example the principles ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The invention, together with objects and advantages thereof, maybest be understood by reference to the following description of thepresently preferred embodiments together with the accompanying drawingsin which:

[0016]FIG. 1 is a cross-sectional view illustrating a swash plate typevariable displacement compressor according to one embodiment of thepresent invention;

[0017]FIG. 2 is a cross-sectional view illustrating the control valveinstalled in the compressor shown in FIG. 1;

[0018]FIG. 3 is a partial cross-sectional view illustrating a controlvalve according to a second embodiment of the present invention;

[0019]FIG. 4 is a partial cross-sectional view illustrating a controlvalve according to a third embodiment of the present invention;

[0020]FIG. 5 is a cross-sectional view illustrating a control valveaccording to a fourth embodiment of the present invention;

[0021]FIG. 6 is a partial cross-sectional view illustrating a prior artcontrol valve; and

[0022]FIG. 7 is a partial cross-sectional view illustrating anotherprior art control valve.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] First to fourth embodiments of a displacement control structureused in a variable displacement swash plate type compressor C will nowbe described. The compressor is installed in a refrigerant circuit of avehicle air conditioner. In the second to fourth embodiments, only theparts different from the first embodiment are explained. Like membersare given the like numbers and detailed explanations are omitted. Thefirst embodiment will now be described.

Variable Displacement Swash Plate Type Compressor

[0024] As shown in FIG. 1, the compressor C has a housing. Thecompressor housing includes a cylinder block 11, a front housing member12, a valve assembly 13, and a rear housing member 14. The front housingmember 12 is secured to the front end (left end as viewed in FIG. 1) ofthe cylinder block 11. The rear housing member 14 is secured to the rearend (right end as viewed in FIG. 1) of the cylinder block 11 with thevalve assembly 13 in between.

[0025] The cylinder block 11 and the front housing member 12 define acrank chamber 15 in between. A drive shaft 16 is rotatably supported inthe crank chamber 15. The drive shaft 16 is coupled to a vehicle engineE, which functions as an external drive source. A lug plate 17 iscoupled to the drive shaft 16 and is located in the crank chamber 15.The lug plate 17 rotates integrally with the drive shaft 16.

[0026] A cam plate, which is a swash plate 18 in the first embodiment,is housed in the crank chamber 15. The swash plate 18 slides along andinclines with respect to the drive shaft 16. A hinge mechanism 19 islocated between the lug plate 17 and the swash plate 18. The hingemechanism 19 causes the swash plate 18 rotate integrally with the lugplate 17 and the drive shaft 16, and permits the swash plate 18 toincline with respect to the drive shaft 16, while sliding on the driveshaft 16 along the axis of the drive shaft 16. The inclination angle ofthe swash plate 18 is represented by an angle formed by the swash plate18 and a plane perpendicular to the axis of the drive shaft 16.

[0027] Cylinder bores 11 a (only one is shown in the drawing) are formedin the cylinder block 11 to surround the drive shaft 16. Each cylinderbore 11 a extends through the cylinder block 11 along the axis of thedrive shaft 16. A single headed piston 20 is accommodated in eachcylinder bore 11 a. The piston 20 reciprocates inside the cylinder bore11 a. The openings of each cylinder bore 11 a are closed by the valveassembly 13 and the corresponding piston 20. A compression chamber 21 isdefined inside each cylinder bore 11 a. The volume of each compressionchamber 21 changes as the corresponding piston 20 reciprocates. Eachpiston 20 is coupled to the peripheral portion of the swash plate 18 bya pair of shoes 22. The shoes 22 convert rotation of the swash plate 18,which rotates with the drive shaft 16, to reciprocation of the pistons20.

[0028] A suction chamber 23 and a discharge chamber 24 are definedbetween the valve assembly 13 and the rear housing member 14. The valveassembly 13 has suction ports 25, suction valve flaps 26, dischargeports 27, and discharge valve flaps 28. Each suction port 25, eachsuction valve flap 26, each discharge port 27, and each discharge valveflap 28 correspond to one of the cylinder bores 11 a. As each piston 20moves from the top dead center to the bottom dead center, refrigerantgas in the suction chamber 23 is drawn into the correspondingcompression chamber 21 through the corresponding suction port 25 whileflexing the suction valve flap 26 to an open position. Refrigerant gasthat is drawn into the compression chamber 21 is compressed to apredetermined pressure as the piston 20 is moved from the bottom deadcenter to the top dead center. Then, the gas is discharged to thedischarge chamber 24 through the corresponding discharge port 27 whileflexing the discharge valve flap 28 to an open position.

Displacement Varying Structure

[0029] The pressure of the crank chamber 15 contributes to control ofthe inclination angle of the swash plate 18 and is controlled by adisplacement varying structure. The displacement varying structureincludes a bleed passage 29, a supply passage 30, and a control valveCV1, which are provided in the compressor housing shown in FIG. 1. Thebleed passage 29 connects the crank chamber 15 with the suction chamber23, which forms part of a suction pressure zone of the refrigerantcircuit. The supply passage 30 connects a discharge pressure zone Pd ofthe refrigerant circuit with the crank chamber 15. The supply passage 30is regulated by the control valve CV1. The control valve CV1 is insertedin and fixed to an accommodation recess 35 formed in the rear housingmember 14.

[0030] Adjusting the opening degree of the control valve CV1 controlsthe ratio between the flow rate of highly pressurized gas supplied tothe crank chamber 15 from the discharge pressure zone Pd through thesupply passage 30 and the flow rate of refrigerant gas conducted fromthe crank chamber 15 to the suction chamber 23 through the bleed passage29. The pressure of the crank chamber 15 is determined, accordingly. Thedifference between the pressure in the crank chamber 15 and the pressurein the compression chambers 21 with the pistons 20 in between is changedaccording to changes in the pressure of the crank chamber 15. Thisalters the inclination angle of the swash plate 18. As a result, thestroke of each piston 20, that is, the displacement of the compressor C,is controlled.

Refrigerant Circuit

[0031] As shown in FIG. 1, the refrigerant circuit of the vehicle airconditioner includes the compressor C and an external refrigerantcircuit G. The external refrigerant circuit G includes a condenser (gascooler) 31, an expansion valve 32, and an evaporator 33. A section ofthe refrigerant circuit from the discharge chamber 24 to the inlet ofthe condenser 31 form the discharge pressure zone Pd.

[0032] A fixed restrictor 34 is provided in the discharge pressure zonePd. As the flow rate of refrigerant in the refrigerant circuitincreases, the pressure difference between a section upstream of thefixed restrictor 34 and a section downstream of the fixed restrictor 34is increased. This pressure difference will be referred to as atwo-point pressure difference. That is, the two-point pressuredifference corresponds to the pressure loss between the section upstreamof the fixed restrictor 34 and the section downstream of the fixedrestrictor 34, and positively correlates with the flow rate in therefrigerant circuit. Therefore, detecting the two-point pressuredifference permits the flow rate of the refrigerant circuit to beindirectly detected.

[0033] The discharge pressure zone Pd of the refrigerant circuitincludes a first pressure zone PdH and a second pressure zone PdL. Thefirst pressure zone PdH is located upstream of the fixed restrictor 34,or at the side corresponding to the discharge chamber 24. The secondpressure zone PdL is located downstream of the fixed restrictor 34, orat the side corresponding to the condenser 31. The pressure of the firstpressure zone PdH is higher than the pressure of the second pressurezone PdL. The pressure of the first pressure zone PdH and the pressureof the second pressure zone PdL are each introduced to the control valveCV1. The supply passage 30 includes an upstream section 30 a upstream ofthe accommodation recess 35 and a downstream section 30 b downstream ofthe accommodation recess 35. The upstream section 30 a is connected tothe second pressure zone PdL.

Control Valve

[0034] As shown in FIG. 2, the control valve CV1 includes an inlet valveportion and a solenoid 60. The inlet valve portion is arranged in anupper portion of the valve CV1, while the solenoid 60 is arranged in alower portion of the valve CV1. The inlet valve portion adjusts theopening degree (throttle amount) of the supply passage 30. The solenoid60 is an electromagnetic actuator for urging a rod 40 located in thecontrol valve CV1 based on a current supplied from an outside source.The rod 40 includes a separation portion 41, a coupler portion 42, avalve body portion 43, and a guide portion 44. The separation portion 41is at the distal end of the rod 40. The diameter of the coupler portion42 is less than that of the separation portion 41. The valve bodyportion 43 is located at a middle portion of the rod 40. The guideportion 44 is located at the proximal end of the rod 40. The valve bodyportion 43 forms part of the guide portion 44.

[0035] The control valve CV1 has a valve housing 45. The housing 45includes a plug 45 a and an upper portion 45 b and a lower portion 45 c.The upper portion 45 b defines the shape of the inlet valve portion. Thelower portion 45 c defines the shape of the solenoid 60. A valve chamber46 is defined in the upper portion 45 b of the valve housing 45. Apressure sensing chamber 48 is defined between the upper portion 45 band the plug 45 a, which is press fitted to the top portion of the upperportion 45 b. The upper portion 45 b includes a separation wall 49located between the valve chamber 46 and the pressure sensing chamber48. A through hole 47 is formed in the separation wall 49. The throughhole 47 extends between the valve chamber 46 and the pressure sensingchamber 48.

[0036] The rod 40 extends through the valve chamber 46 and the throughhole 47. The rod 40 moves in the axial direction of the control valveCV1, or in the vertical direction as viewed in FIG. 2. The separationportion 41 of the rod 40 is slidably inserted in the through hole 47 andseparates the through hole 47 from the pressure sensing chamber 48. Thediameter of the coupler portion 42 of the rod 40 is less than that ofthe through hole 47 and permits the valve chamber 46 to communicate withthe through hole 47.

[0037] A space 50 is defined between an outer surface 45 d of the upperportion 45 b and an inner surface 35 a of the accommodation recess 35 ofthe rear housing member 14. The space 50 is divided into a firstconnecting chamber 50 a and a second connecting chamber 50 b by a firstseal member 68 provided about the upper portion 45 b. The secondconnecting chamber 50 b is closer to the opening of the accommodationrecess 35 than the first connecting chamber 50 a. That is, the secondconnecting chamber 50 b is located below the first connecting chamber 50a as viewed in FIG. 2. The second connecting chamber 50 b isdisconnected from the outside air by a second seal member 69 providedabout the lower portion 45 c.

[0038] The bottom of the valve chamber 46 is formed by the upper surfaceof a fixed iron core 62. A radially extending first port 51 is formed inthe wall surrounding the valve chamber 46 of the upper portion 45 b. Thefirst port 51 connects the second connecting chamber 50 b with the valvechamber 46. Therefore, the valve chamber 46 is connected to the crankchamber 15 through the first port 51, the second connecting chamber 50b, and the downstream section 30 b of the supply passage 30.

[0039] A radially extending second port 52 is formed in the separationwall 49 surrounding the through hole 47 of the upper portion 45 b. Thesecond port 52 connects the first connecting chamber 50 a with a portion47 a of the through hole 47 that is close to the valve chamber 46.Therefore, the portion 47 a of the through hole 47 closer to the valvechamber 46 is connected to the second pressure zone PdL through thesecond port 52, the first connecting chamber 50 a, and the upstreamsection 30 a of the supply passage 30.

[0040] That is, the first port 51, the valve chamber 46, the throughhole 47, and the second port 52 function as an internal passage of thecontrol valve CV1 and as part of the supply passage 30 connecting thesecond pressure zone PdL and the crank chamber 15.

[0041] The valve body portion 43 of the rod 40 is located in the valvechamber 46. A step defined between the valve chamber 46 and the throughhole 47 forms a valve seat 53. A portion 47 a of the through hole 47adjacent to the valve chamber 46 functions as a valve hole. The rod 40shown in FIG. 2 is located at the lowermost position. When the rod 40 ismoved from the lowermost position to the uppermost position, where thevalve body portion 43 contacts the valve seat 53, the valve hole 47 a isclosed. The valve body portion 43 of the rod 40 is an inlet valve bodythat controls the opening degree of the supply passage 30.

[0042] A pressure sensing member 54, which is a bellows, is located inthe pressure sensing chamber 48. The upper end of the pressure sensingmember 54 is fixed to the plug 45 a of the valve housing 45. Thepressure sensing member 54 is shaped as a cylinder with a closed end.The pressure sensing member 54 divides the pressure sensing chamber 48into a first chamber 55, which is the interior of the pressure sensingmember 54, and a second chamber 56, which is the exterior of thepressure sensing member 54. The second chamber 56 is located closer tothe valve chamber 46 compared to the first chamber 55 and is connectedto the valve chamber 46 by the through hole 47. The second chamber 56 isadjacent to the valve hole 47 a with the separation portion 41 of therod 40 in between. The lower end of the pressure sensing member 54 isdisplaced in accordance with the pressure difference between the firstchamber 55 and the second chamber 56. A recess is formed at the lowerend of the pressure sensing member 54. The recess functions as a rodreceiving portion 54 a. The separation portion 41 of the rod 40 isinserted in and press fitted to the rod receiving portion 54 a.

[0043] The first chamber 55 is connected to the discharge chamber 24through a third port 57 formed in the plug 45 a, and a pressureintroduction passage 37 formed in the rear housing member 14. Thedischarge chamber 24 forms a part of the first pressure zone PdH. Afourth port 58 is formed in a circumferential wall of the upper portion45 b of the valve housing 45 that surrounds the first chamber 55. Thesecond chamber 56 is connected to the second pressure zone PdL throughthe fourth port 58, the first connecting chamber 50 a, and the upstreamsection 30 a of the supply passage 30. Therefore, the pressuredifference between the first chamber 55 and the second chamber 56 isequal to the two-point pressure difference in the refrigerant circuit,which is the pressure difference between the first pressure zone PdH andthe second pressure zone PdL.

[0044] The first connecting chamber 50 a connects the second port 52with the fourth port 58. That is, the passage from the second pressurezone PdL to the control valve CV1 branches at the first connectingchamber 50 a. The branched portions are connected to the second chamber56 and the valve hole 47 a. In other words, part of the passageconnecting the second chamber 56 to the second pressure zone PdL andpart of the passage connecting the valve hole 47 a to the secondpressure zone PdL both include the upstream section 30 a of the supplypassage 30 and the first connecting chamber 50 a.

[0045] That is, if one of the valve hole 47 a and the valve chamber 46that is adjacent to the second chamber 56 with the separation portion 41in between is defined as an adjacent zone, the adjacent zone is thevalve hole 47 a in this embodiment. The second chamber 56 and the valvehole 47 a are both connected to a common pressure zone in therefrigerant circuit, or to the second pressure zone PdL.

[0046] The solenoid 60 includes an accommodation cylinder 61 that has aclosed end. The fixed iron core 62 is fitted to the upper portion of theaccommodation cylinder 61. Accordingly, a solenoid chamber 63 is definedin a lower portion of the accommodation cylinder 61. A movable iron core64 is located in the solenoid chamber 63. The movable iron core 64 ismovable along the axial direction of the control valve CV1. A guide hole62 a is formed in the center of the fixed iron core 62. The guide hole62 a extends along the axial direction of the control valve CV1. Theguide portion 44 of the rod 40 is received by the guide hole 62 a. Theguide portion 44 is movable in the axial direction of the control valveCV1. The lower end of the guide portion 44 abuts against the movableiron core 64 in the solenoid chamber 63.

[0047] A valve body urging spring 66 is accommodated in the solenoidchamber 63. The valve body urging spring 66 urges the movable iron core64 toward the fixed iron core 62, thereby urging the rod 40 (the valvebody portion 43) upward as viewed in the drawing. Therefore, the movableiron core 64 and the rod 40 integrally move vertically.

[0048] A coil 67 is wound about the fixed iron core 62 and the movableiron core 64. The coil 67 receives drive signals based on commands thatare sent from an air conditioner ECU (not shown) according to parameterssuch as thermal load. The coil 67 generates an electromagneticattraction force (electromagnetic urging force) between the movable ironcore 64 and the fixed iron core 62. The magnitude of the generated forcecorresponds to the value of the supplied current per unit time.

[0049] A target value sought in a control of the two-point pressuredifference, or a target pressure difference as an operation reference,is determined by the amount of current supplied to the coil 67. Thepressure sensing member 54 automatically determines the axial positionof the rod 40 (the valve body portion 43) according to the two-pointpressure difference such that the target pressure difference ismaintained.

[0050] For example, if the flow rate of the refrigerant in therefrigerant circuit is decreased due to a decrease in the rotation speedof the engine E, that is, if the two-point pressure difference isdecreased from the target pressure difference, the downward forceapplied to the rod 40 by the pressure sensing member 54 based on thetwo-point pressure difference decreases. If the upward electromagneticforce of the solenoid 60 is not changed from the value at the time, theupward and downward forces acting on the rod 40 are not balanced. Thus,the rod 40 (the valve body portion 43) moves upward to decrease theopening degree of the valve hole 47 a, which lowers the pressure in thecrank chamber 15. Accordingly, the inclination angle of the swash plate18 is increased, and the displacement of the compressor C is increased.The increase in the displacement of the compressor C increases the flowrate of refrigerant in the refrigerant circuit. This increases thetwo-point pressure difference in the refrigerant circuit so that thepressure difference seeks the target pressure difference.

[0051] If the flow rate of the refrigerant in the refrigerant circuit isincreased due to an increase in the rotation speed of the engine E, thatis, if the two-point pressure difference is increased from the targetpressure difference, the downward force applied to the rod 40 by thepressure sensing member 54 based on the two-point pressure differenceincreases. If the upward electromagnetic force of the solenoid 60 is notchanged from the value at the time, the upward and downward forcesacting on the rod 40 are not balanced. Thus, the rod 40 (the valve bodyportion 43) moves downward to increase the opening degree of the valvehole 47 a, which raises the pressure in the crank chamber 15.Accordingly, the inclination angle of the swash plate 18 is decreased,and the displacement of the compressor C is decreased. The decrease inthe displacement of the compressor C decreases the flow rate ofrefrigerant in the refrigerant circuit. This decreases the two-pointpressure difference in the refrigerant circuit so that the pressuredifference seeks the target pressure difference.

[0052] The target pressure difference can be externally changed byadjusting the amount of electricity supplied to the coil 67. Forexample, if the amount of electricity supplied to the coil 67 isincreased, the upward electromagnetic force applied to the rod 40 by thesolenoid 60 is increased. In this case, if the force of the pressuresensing member 54 based on the two-point pressure difference is notchanged, the upward force and the downward force acting on the rod 40are not balanced. Accordingly, the rod 40 (the valve body portion 43) ismoved upward to decrease the opening degree of the valve hole 47 a, andthe displacement of the compressor C is increased. As a result, the flowrate of refrigerant in the refrigerant circuit increases. This increasesthe two-point pressure difference in the refrigerant circuit. That is,increasing the amount of electricity supplied to the coil 67 increasesthe target pressure difference.

[0053] If the amount of electricity supplied to the coil 67 isdecreased, the upward electromagnetic force applied to the rod 40 by thesolenoid 60 is decreased. In this case, if the force of the pressuresensing member 54 based on the two-point pressure difference is notchanged, the upward force and the downward force acting on the rod 40are not balanced. Accordingly, the rod 40 (the valve body portion 43) ismoved downward to increase the opening degree of the valve hole 47 a,and the displacement of the compressor C is decreased. As a result, theflow rate of refrigerant in the refrigerant circuit decreases. Thisdecreases the two-point pressure difference in the refrigerant circuit.That is, decreasing the amount of electricity supplied to the coil 67decreases the target pressure difference.

[0054] The present embodiment has the following advantages.

[0055] (1) In the control valve CV1, the separation portion 41 of therod 40 disconnects the valve chamber 46 from the second chamber 56through the through hole 47. Therefore, the pressure of the secondchamber 56 is not directly affected by changes in the opening degree ofthe valve body portion 43. This prevents the pressure in the secondchamber 56 from being fluctuated by changes in the valve opening degree.Thus, the pressure sensing member 54 accurately determines the positionof the rod 40 (the valve body portion 43) without being affected bychanges in the valve opening degree. Accordingly, the pressuredisplacement is accurately controlled.

[0056] The second chamber 56 of the control valve CV1 and the valve hole47 a, which is adjacent to the second chamber 56 with the separationportion 41 in between, are both connected to the second pressure zonePdL. This configuration prevents the pressure of the valve hole 47 a andthe pressure of the second chamber 56 from differing from each other.Therefore, the entry of foreign particles to the sliding portions of thethrough hole 47 and the rod 40 (the separation portion 41) due to thepressure difference between the valve hole 47 a and the second chamber56 is prevented. The rod 40 is therefore prevented from malfunctioningdue to foreign particles.

[0057] As described above, this embodiment prevents the rod 40 frommalfunctioning and also prevents the controllability of the compressordisplacement from deteriorating.

[0058] (2) The fixed restrictor 34 is provided in the discharge pressurezone Pd. The section upstream of the fixed restrictor 34 is the firstpressure zone PdH, and the section downstream of the fixed restrictor 34is the second pressure zone PdL. The two-point pressure difference,which is the pressure difference between the section upstream of thefixed restrictor 34 and the section downstream of the fixed restrictor34, is greater than a pressure difference caused by the passageresistance in a passage having no restrictor. Therefore, the controlvalve CV1, which operates by detecting the two-point pressuredifference, accurately reflects changes in the refrigerant flow ratewhen determining the position of the rod 40 (the valve body portion 43).The control valve CV1 thus accurately controls the displacement of thecompressor C.

[0059] Although the pressure in the section upstream of the fixedrestrictor 34 and the pressure in the section downstream of the fixedrestrictor 34 are pressures in the discharge pressure zone Pd, these twopressures upstream and downstream of the restrictor 34 are greatlydifferent from each other in some cases. Therefore, connecting thesecond chamber 56 and the valve hole 47 a, which are adjacent to eachother with the separation portion 41 in between, to the second pressurezone PdL, or to the section downstream of the fixed restrictor 34, isparticularly advantageous to provide the above advantage (prevention ofmalfunction of the rod 40).

[0060] (3) The valve housing 45 of the control valve CV1 is inserted inthe accommodation recess 35 formed in the rear housing member 14. Thesecond chamber 56 is connected to the valve hole 47 a through the firstconnecting chamber 50 a, which is a space defined between the innersurface 35 a of the accommodation recess 35 and the outer surface 45 dof the valve housing 45. Therefore, only one passage is required forconnecting the second pressure zone PdL with the first connectingchamber 50 a. Thus, for example, compared to a case in which the secondchamber 56 and the valve hole 47 a are each connected to the secondpressure zone PdL through an independent passage, respectively, thestructure is simplified.

[0061] The first connecting chamber 50 a has a relatively large volume.This lessens the influences of pressure fluctuations caused by changesin the valve opening degree of the valve hole 47 a to the second chamber56. Further, the second chamber 56 is connected to the valve hole 47 athrough the first connecting chamber 50 a located outside of the valvehousing 45. This structure extends the length of the passage between thesecond chamber 56 and the valve hole 47 a. This configuration reliablyprevents the pressure of the second chamber 56 from being directlyinfluenced by changes in the valve opening degree.

[0062] (4) The control valve CV1 has the solenoid 60, which is anelectromagnetic actuator. As stated in the prior art section, in acontrol valve having an electromagnetic actuator, adopting a structurethat completely opens the entire through hole 47 as a part of the supplypassage 30 worsens the controllability of the displacement. Thus, in thecontrol valve CV1 having the solenoid 60, blocking the connectionbetween the valve chamber 46 and the second chamber 56 through thethrough hole 47 with the separation portion 41 of the rod 40 isparticularly advantageous to improve the controllability of thedisplacement.

[0063] A second embodiment of the present invention will now bedescribed. As shown in FIG. 3, a control valve CV2 of the secondembodiment is the same as the control valve CV1 of the first embodimentexcept for that the fourth port 58 is omitted. The second chamber 56 isconnected to the second port 52 through a hole 71 formed in theseparation wall 49. Therefore, the pressure of the second pressure zonePdL is introduced to the second chamber 56 through the second port 52and the hole 71. That is, the second port 52 and the hole 71 form aconnecting passage. The connecting passage (the second port 52 and thehole 71) connects the second chamber 56 with the valve hole 47 a withinthe valve housing 45.

[0064] The second embodiment provides the same advantages as (1), (2)and (4) of the first embodiment. Other than these advantages, the secondembodiment has the following advantages. That is, the second chamber 56and the valve hole 47 a are connected to each other within the valvehousing 45 through the connecting passage (the second port 52 and thehole 71). Thus, only one passage, which is connected to the valve hole47 a, is required for connecting the second pressure zone PdL to thecontrol valve CV2. Thus, for example, compared to a case in which thesecond chamber 56 and the valve hole 47 a are each connected to thesecond pressure zone PdL through an independent passage, respectively,the structure is simplified.

[0065] For example, compared to the first embodiment, in which thesecond chamber 56 and the valve hole 47 a are connected to each otherthrough the space defined by the inner surface 35 a of the accommodationrecess 35 and the outer surface 45 d of the valve housing 45, that isthe first connecting chamber 50 a, no great space needs to be createdbetween the inner surface 35 a of the accommodation recess 35 and theouter surface 45 d of the valve housing 45. Therefore, the inner surface35 a of the accommodation recess 35 are brought into close contact withthe outer surface 45 d of the valve housing 45 in a relatively largearea. This permits the rear housing member 14 of the compressor C tostably support the control valve CV2.

[0066] A third embodiment of the present invention will now bedescribed. As shown in FIG. 4, a control valve CV3 of the thirdembodiment is the same as the control valve CV1 of the first embodimentexcept for that the opening degree of the bleed passage 29, not theopening degree of the supply passage 30, is adjusted. The supply passage30 is always open. The control valve CV3 adjusts the opening degree ofthe bleed passage 29, thereby changing the flow rate of refrigerant gasconducted to the suction chamber 23 from the crank chamber 15 throughthe bleed passage 29. As a result, the pressure of the crank chamber 15is adjusted, and the displacement of the compressor C is controlled,accordingly.

[0067] Unlike the control valve CV1 of the first embodiment, the firstchamber 55 and the second chamber 56 forming the pressure sensingchamber 48 of the control valve CV3 according to the third embodimentare connected to a suction pressure zone Ps of the refrigerant circuit.

[0068] A section of the refrigerant circuit from the outlet of theevaporator 33 to the suction chamber 23 of the compressor forms thesuction pressure zone Ps. A fixed restrictor 91 is provided in thesuction pressure zone Ps. The suction pressure zone Ps includes a firstpressure zone PsH and a second pressure zone PsL. The first pressurezone PsH is located upstream of the fixed restrictor 91, or at the sidecorresponding to the evaporator 33. The second pressure zone PsL islocated downstream of the fixed restrictor 91, or at the sidecorresponding to the suction chamber 23. The pressure of the firstpressure zone PsH is higher than the pressure of the second pressurezone PsL. The pressure of the first pressure zone PsH is introduced tothe first chamber 55 through a pressure introduction passage 92 formedin the rear housing member 14 and the third port 57. The bleed passage29 includes an upstream section 29 a upstream of the accommodationrecess 35 and a downstream section 29 b downstream of the accommodationrecess 35. The suction chamber 23 forms a part of the second pressurezone PsL. The pressure of the suction chamber 23 is introduced to thesecond chamber 56 through the downstream section 29 b, the firstconnecting chamber 50 a, and the fourth port 58.

[0069] An inner connecting chamber 94 and a valve accommodating hole 95are defined in the upper portion 45 b of the control valve CV3. Thevalve accommodating hole 95 functions as a valve chamber and a throughhole. The inner connecting chamber 94 and the valve accommodating hole95 are connected to each other by a connecting passage 96 that has asmaller cross-sectional area than the valve accommodating hole 95. Therod 40 is movably provided in the inner connecting chamber 94, theconnecting passage 96, and the valve accommodating hole 95. Theseparation portion 41 of the rod 40 is slidably inserted in the valveaccommodating hole 95 and separates the valve accommodating hole 95 fromthe pressure sensing chamber 48. The diameter of the coupler portion 42of the rod 40 is less than that of the connecting passage 96 and permitsthe inner connecting chamber 94 to communicate with the valveaccommodating hole 95.

[0070] In this embodiment, the valve body portion 43 forms part of theseparation portion 41. The valve body portion 43 is located in the valveaccommodating hole 95. A step defined between the valve accommodatinghole 95 and the connecting passage 96 forms the valve seat 53. Theconnecting passage 96 functions as a valve hole.

[0071] The inner connecting chamber 94 is connected to the crank chamber15 through the first port 51, the second connecting chamber 50 b, andthe upstream section 29 a of the bleed passage 29. Part of the valveaccommodating hole 95 that is closer to the inner connecting chamber 94will be referred to a valve body accommodating portion 95 a. The valvebody accommodating portion 95 a is adjacent to second chamber 56 withthe separation portion 41 in between. The valve body accommodatingportion 95 a is connected to the suction chamber 23 through the secondport 52, the first connecting chamber 50 a, and the downstream section29 b of the bleed passage 29. That is, the second chamber 56 and thevalve body accommodating portion 95 a of the valve accommodating hole 95are both connected to a common pressure zone in the refrigerant circuit,or to the second pressure zone PsL.

[0072] As the flow rate of refrigerant in the refrigerant circuitincreases, the difference between a section upstream of the fixedrestrictor 91 and a section downstream of the fixed restrictor 91, orthe two-point pressure difference, is increased. That is, the two-pointpressure difference corresponds to the pressure loss between the sectionupstream of the fixed restrictor 91 and the section downstream of thefixed restrictor 34, and positively correlates with the flow rate in therefrigerant circuit. Therefore, the control valve CV3 of this embodimentoperates in the same manner as the control valve CV1 of the firstembodiment. That is, the control valve CV3 adjusts the opening degree ofthe bleed passage 29 such that the displacement of the compressor ischanged to cancel fluctuations of the refrigerant flow rate.

[0073] The third embodiment provides the same advantages as (1) to (4)of the first embodiment.

[0074] A fourth embodiment of the present invention will now bedescribed. As shown in FIG. 5, a control valve CV4 of the fourthembodiment is the same as the control valve CV1 of the first embodimentexcept for that the solenoid 60 is omitted. Further, the control valveCV4 controls the opening degree of the bleed passage 29, but not theopening degree of the supply passage 30.

[0075] That is, in the fourth embodiment, the valve chamber 46 is a partof the bleed passage 29 that is located in the control valve CV4. Thevalve chamber 46 accommodates a valve body 75 attached to the rod 40.The valve body 75 can be displaced in the valve chamber 46. The pressuresensing member 54 and the valve body 75 are coupled to each other withthe rod 40. A valve hole 76, which forms part of the bleed passage 29,is spaced apart from the through hole 47. Specifically, the valve hole76 is connected to the valve chamber 46 at a part opposite from the partcorresponding to the through hole 47 with respect to the valve body 75.

[0076] The second chamber 56 of the control valve CV4 is connected tothe suction chamber 23 through a port 80 formed in the valve housing 45,and a pressure introducing passage 77 formed in the rear housing member14. The first chamber 55 is either exposed to the atmosphere or is in avacuum. That is, the internal pressure of the first chamber 55 ismaintained to a substantially constant reference pressure. The valvechamber 46 is connected to the suction chamber 23 through a port 81formed in the valve housing 45, and the downstream section 29 b of thebleed passage 29. The valve hole 76 is connected to the crank chamber 15through a port 82 formed in the valve housing 45, and the upstreamsection 29 a of the bleed passage 29. That is, the second chamber 56 andthe valve chamber 46, which are adjacent to each other with theseparation portion 41 of the rod 40 in between, are both exposed to thepressure of the suction chamber 23, which forms part of the suctionpressure zone.

[0077] In other words, in the fourth embodiment, the valve chamber 46 isthe adjacent zone, which is adjacent to the second chamber 56 with theseparation portion 41 in between. The second chamber 56 and the valvehole 47 a are both connected to a common pressure zone in therefrigerant circuit, or to the suction chamber 23.

[0078] The downstream section 29 b of the bleed passage 29 and thepressure introducing passage 77 may be separately formed or have acommon section. As in the first embodiment, the space 50 may be definedbetween the outer surface 45 d of the valve housing 45 and the innersurface of the accommodation recess 35, and the valve chamber 46 may beconnected to the second chamber 56 through the space 50 (see FIG. 2).Alternatively, as in the second embodiment, the hole 71 may be formed inthe separation wall 49, and the valve chamber 46 and the second chamber56 may be connected to each other through the hole 71 within the valvehousing 45 (see FIG. 3).

[0079] In the compressor of fourth embodiment, highly pressurizeddischarge refrigerant gas is supplied from the discharge chamber 24 tothe crank chamber 15 through the supply passage 30. On the other hand,to maintain the pressure of the suction chamber 23 at a constant level,the pressure sensing member 54 of the control valve CV4 is displaced inaccordance with the difference between the pressure of the suctionchamber 23, which is introduced to the second chamber 56 through thepressure introducing passage 77, and the reference pressure in the firstchamber 55 to determine the axial position of the valve body 75.Accordingly, the opening degree of the valve hole 76 is adjusted. Thecontrol valve CV4 adjusts the opening degree of the bleed passage 29,thereby changing the flow rate of refrigerant gas conducted to thesuction chamber 23 from the crank chamber 15 through the bleed passage29. As a result, the pressure of the crank chamber 15 is adjusted, andthe displacement of the compressor C is controlled, accordingly.

[0080] For example, when the temperature of the passenger compartmentincreases, the cooling load increases. This increases the pressure inthe suction chamber 23. Accordingly, the pressure difference between thesecond chamber 56 and the first chamber 55 in the control valve CV4 isincreased. Therefore, the pressure sensing member 54 is displaceddownward as viewed in the drawing against the reference pressure of thefirst chamber 55 and the force of the urging spring 78, which is locatedin the pressure sensing member 54 and urges the valve body 75 toward thevalve seat 53 through the rod 40. Accordingly, the valve body 75 isdisplaced to increase the valve opening, and the pressure in the crankchamber 15 is lowered. Accordingly the displacement of the compressor Cis increased. The increase in the compressor displacement lowers thesuction pressure in the suction chamber 23.

[0081] When the temperature of the passenger compartment decreases, thecooling load decreases. This decreases the suction pressure in thesuction chamber 23. Accordingly, the pressure difference between thesecond chamber 56 and the first chamber 55 in the control valve CV4 isdecreased. Therefore, the pressure sensing member 54 is displaced upwardas viewed in the drawing by the reference pressure of the first chamber55 and the force of the urging spring 78. Accordingly, the valve body 75is displaced to decrease the valve opening, and the pressure in thecrank chamber 15 is raised. Accordingly the displacement of thecompressor C is decreased. The decrease in the compressor displacementraises the suction pressure in the suction chamber 23.

[0082] The fourth embodiment provides the same advantage as (1) of thefirst embodiment.

[0083] The present invention may be embodied in the following formswithout departing from the spirit or scope of the invention.

[0084] In the first to third embodiments, the solenoid 60 may be omittedfrom the control valves CV1 to CV3 so that the control valves CV1 to CV3are simple pressure sensing valves that are not capable of beingexternally controlled.

[0085] In the fourth embodiment, a solenoid may be added to the controlvalve CV4, so that the control valve CV4 is a pressure sensing valvethat is capable of being externally controlled. In this case, thepressure sensing member 54 of the control valve CV4 is automaticallydisplaced according to fluctuations in the suction pressure to determinethe axial position of the valve body 75, such that a target value of thesuction pressure, which is determined by the amount of electricitysupplied to the solenoid, is maintained. That is, the pressure sensingmember 54 is displaced such that the target suction pressure as theoperation reference is maintained. The target suction pressure can beexternally changed by adjusting the amount of electricity supplied tothe solenoid.

[0086] In the control valves CV1 and CV2 of the first and secondembodiments, the first chamber 55 is exposed to the pressure of thefirst pressure zone PdH, which is a higher pressure section of thedischarge pressure zone Pd, and the second chamber 56 and the valve hole47 a are each exposed to the pressure of the second pressure zone PdL,which is a lower pressure section of the discharge pressure zone Pd. Inthe control valve CV3 of the third embodiment, the first chamber 55 isexposed to the pressure of the first pressure zone PsH, which is ahigher pressure section of the suction pressure zone Ps, and the secondchamber 56 and the valve body accommodating portion 95 a, which is avalve chamber, are each exposed to the pressure of the second pressurezone PsL, which is a lower pressure section of the suction pressure zonePs. That is, in the first to third embodiments, the pressure of thefirst chamber 55 is higher than those of the second chamber 56 and theadjacent zone (the valve hole 47 a and the valve body accommodatingportion 95 a). However, the pressure of the first chamber 55 may belower than those of the second chamber and the adjacent zone. That is,the first chamber 55 of the control valves may be exposed to thepressure of the second pressure zone, and the second chamber 56 and theadjacent zone may be exposed to the pressure of the first pressure zone.

[0087] In the control valves CV1 to CV3 of the first to thirdembodiments, setting the pressure of the first chamber higher than thepressure of the second chamber reverses the direction of displacement ofthe pressure sensing member 54 based on the pressure difference betweenthe first chamber 55 and the second chamber 56. Therefore, in themodifications of the first and second embodiments, the arrangement ofthe valve hole and the valve chamber with respect to the pressuresensing chamber 48 needs to be inverted so that an increase in thepressure difference between the first and second chambers 55, 56displaces the valve body portion 43 to increase the valve openingdegree. That is, the second chamber 56 and the valve chamber 46 arearranged to be adjacent to each other with the separation portion 41 inbetween. In the modification of the third embodiment, the arrangement ofthe valve hole and the valve chamber with respect to the pressuresensing chamber 48 needs to be inverted so that an increase in thepressure difference between the first and second chambers 55, 56displaces the valve body to decrease the valve opening degree. That is,the second chamber 56 and the valve hole are arranged to be adjacent toeach other with the separation portion 41 in between.

[0088] Therefore, the present examples and embodiments are to beconsidered as illustrative and not restrictive and the invention is notto be limited to the details given herein, but may be modified withinthe scope and equivalence of the appended claims.

1. A displacement varying structure of a variable displacementcompressor that is installed in a refrigerant circuit, wherein therefrigerant circuit has a discharge pressure zone and a suction pressurezone, wherein the variable displacement compressor has a crank chamber,and wherein the displacement varying structure is capable of varying adisplacement of the variable displacement compressor by changing apressure of the crank chamber, the displacement varying structurecomprising: a supply passage for connecting the crank chamber with thedischarge pressure zone; a bleed passage for connecting the crankchamber with the suction pressure zone; and a control valve located in acontrol passage, the control passage being one of the supply passage andthe bleed passage, wherein the control valve includes: a valve housingdefining a valve chamber, a valve hole, and a pressure sensing chamber,wherein the valve chamber and the valve hole form a part of the controlpassage; a valve body accommodated in the valve chamber, wherein thevalve body is capable of being displaced, and wherein the valve bodyadjusts an opening degree of the valve hole in accordance with theposition of the valve body in the valve chamber; a pressure sensingmember accommodated in the pressure sensing chamber, wherein thepressure sensing member divides the pressure sensing chamber into afirst chamber and a second chamber, and wherein the pressure sensingmember is capable of being displaced in accordance with a pressuredifference between the first chamber and the second chamber; aseparation wall that separates in the valve housing the valve chamberand the pressure sensing chamber from each other, wherein the separationwall has a through hole for connecting the valve chamber and the secondchamber with each other; a rod that extends through the through hole andconnects the pressure sensing member and the vale body with each other,wherein the rod has a separation portion that blocks connection betweenthe valve chamber and the second chamber through the through hole; andan adjacent zone that is adjacent to the second chamber with theseparation portion in between, wherein, if a part of the through holethat is closer to the valve chamber than the separation portion andopens to the valve chamber forms the valve hole, the valve hole is theadjacent zone, and if the valve hole is located at the opposite side ofthe valve chamber with respect to the second chamber, the valve chamberis the adjacent zone, and wherein the adjacent zone and the secondchamber are connected to a common pressure zone in the refrigerantcircuit.
 2. The displacement varying structure according to claim 1,wherein the control passage is the supply passage, and the dischargepressure zone includes a first pressure zone and a second pressure zone,wherein the pressure of the first pressure zone is higher than thepressure of the second pressure zone, and wherein the first chamber isconnected to one of the first and second pressure zones, and the secondchamber and the adjacent zone are connected to the other one of thefirst and second pressure zones.
 3. The displacement varying structureaccording to claim 2, wherein a restrictor is provided in the dischargepressure zone, and wherein a section of the discharge pressure zone thatis upstream of the restrictor comprises the first pressure zone, and asection of the discharge pressure zone that is downstream of therestrictor comprises the second pressure zone.
 4. The displacementvarying structure according to claim 1, wherein the control passage isthe bleed passage, and the suction pressure zone includes a firstpressure zone and a second pressure zone, wherein the pressure of thefirst pressure zone is higher than the pressure of the second pressurezone, and wherein the first chamber is connected to one of the first andsecond pressure zones, and the second chamber and the adjacent zone areconnected to the other one of the first and second pressure zones. 5.The displacement varying structure according to claim 4, wherein arestrictor is provided in the suction pressure zone, and wherein asection of the suction pressure zone that is upstream of the restrictorcomprises the first pressure zone, and a section of the suction pressurezone that is downstream of the restrictor comprises the second pressurezone.
 6. The displacement varying structure according to claim 1,wherein the compressor has a compressor housing in which anaccommodation recess is formed, wherein the control valve is inserted inthe accommodation recess, and wherein the second chamber and theadjacent zone are connected to each other through a space definedbetween an inner surface of the accommodation recess and an outersurface of the valve housing.
 7. The displacement varying structureaccording to claim 1, wherein a connecting passage for connecting thesecond chamber to the adjacent zone is formed in the valve housing. 8.The displacement varying structure according to claim 1, wherein thecontrol valve has an actuator, and wherein, based on an externalcommand, the actuator changes a force applied to the valve body.
 9. Arefrigerant-circuit containing a variable displacement compressor,wherein the variable displacement compressor has a crank chamber, and adisplacement of the variable displacement compressor is varied bychanging a pressure of the crank chamber, the refrigerant circuitcomprising: a discharge pressure zone; a suction pressure zone; a supplypassage for connecting the crank chamber with the discharge pressurezone; a bleed passage for connecting the crank chamber with the suctionpressure zone; and a control valve located in a control passage, thecontrol passage being one of the supply passage and the bleed passage,wherein the control valve includes: a valve housing defining a valvechamber, a valve hole, and a pressure sensing chamber, wherein the valvechamber and the valve hole form a part of the control passage; a valvebody accommodated in the valve chamber, wherein the valve body iscapable of being displaced, and wherein the valve body adjusts anopening degree of the valve hole in accordance with the position of thevalve body in the valve chamber; a pressure sensing member accommodatedin the pressure sensing chamber, wherein the pressure sensing memberdivides the pressure sensing chamber into a first chamber and a secondchamber, and wherein the pressure sensing member is capable of beingdisplaced in accordance with a pressure difference between the firstchamber and the second chamber; a separation wall that separates in thevalve housing the valve chamber and the pressure sensing chamber fromeach other, wherein the separation wall has a through hole forconnecting the valve chamber and the second chamber with each other; anda rod that extends through the through hole and connects the pressuresensing member and the vale body with each other, wherein the rod has aseparation portion that blocks connection between the valve chamber andthe second chamber through the through hole, wherein a part of thethrough hole that is closer to the valve chamber than the separationportion and opens to the valve chamber forms the valve hole, and whereinthe valve hole and the second chamber are connected to a common pressurezone in the refrigerant circuit.
 10. The refrigerant circuit accordingto claim 9, wherein the control passage is the supply passage, and thedischarge pressure zone includes a first pressure zone and a secondpressure zone, wherein the pressure of the first pressure zone is higherthan the pressure of the second pressure zone, and wherein the firstchamber is connected to one of the first and second pressure zones, andthe second chamber and the valve hole are connected to the other one ofthe first and second pressure zones.
 11. The refrigerant circuitaccording to claim 10, wherein a restrictor is provided in the dischargepressure zone, and wherein a section of the discharge pressure zone thatis upstream of the restrictor comprises the first pressure zone, and asection of the discharge pressure zone that is downstream of therestrictor comprises the second pressure zone.
 12. The refrigerantcircuit according to claim 9, wherein the control passage is the bleedpassage, and the suction pressure zone includes a first pressure zoneand a second pressure zone, wherein the pressure of the first pressurezone is higher than the pressure of the second pressure zone, andwherein the first chamber is connected to one of the first and secondpressure zones, and the second chamber and the valve hole are connectedto the other one of the first and second pressure zones.
 13. Therefrigerant circuit according to claim 12, wherein a restrictor isprovided in the suction pressure zone, and wherein a section of thesuction pressure zone that is upstream of the restrictor comprises thefirst pressure zone, and a section of the suction pressure zone that isdownstream of the restrictor comprises the second pressure zone.
 14. Therefrigerant circuit according to claim 9, wherein the compressor has acompressor housing in which an accommodation recess is formed, whereinthe control valve is inserted in the accommodation recess, and whereinthe second chamber and the valve hole are connected to each otherthrough a space defined between an inner surface of the accommodationrecess and an outer surface of the valve housing.
 15. The refrigerantcircuit according to claim 9, wherein a connecting passage forconnecting the second chamber to the valve hole is formed in the valvehousing.
 16. The refrigerant circuit according to claim 9, wherein thecontrol valve has an actuator, and wherein, based on an externalcommand, the actuator changes a force applied to the valve body.